Fuel Pump Electrical Problem.
Thread Starter
Drifting
Joined: Apr 2008
Posts: 1,687
Likes: 86
From: De Pere, WI
Fuel Pump Electrical Problem.
So recently, my '00 started dying after running about 15 mins and wouldn't restart for about 5 mins or more. I have been able to rule out all relays and fuses as well as the fuel pump....Now for the part that is confusing the hell out of me.
I have determined that the pump power wire is losing power. will stay without power for a while then suddenly have power again. Now what confuses me - when you unplug the connector from the tank, power returns to the wire but when you plug it back in the power is gone....does it even if the relay pins in the power distribution panel are jumped. I do not have access to a Tech II to see if the PCM is commanding fuel pump on or not.
Any suggestions?
I have determined that the pump power wire is losing power. will stay without power for a while then suddenly have power again. Now what confuses me - when you unplug the connector from the tank, power returns to the wire but when you plug it back in the power is gone....does it even if the relay pins in the power distribution panel are jumped. I do not have access to a Tech II to see if the PCM is commanding fuel pump on or not.
Any suggestions?
Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 302
From: Columbia SC
Sounds like the pump being connected is drawing enough current to cause an open circuit in the harness somewhere. Sure sounds like a wiring issue. I can provide you info on how to help figure this out but not at home now. I believe the PCM grounds the relay to power the pump.
Mr. Sam
Mr. Sam
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Take a look at this schematic. Look at the FUSE and see where it gets its power from... It says (HOT IN RUN AND START)
That power comes from the IGNITION SWITCH.
My guess is, You have dirty /burnt ignition switch contacts. You can remove the switch and clean and rebent the arms for more contact pressure or just buy a new switch
When the car DIES, actually measure the voltage at the two test points on top of the fuse to ground and see if it read LOW. It SHOULD read battery voltage when ever the key is on.
Here is my post on ignition switch repair:
- C5 ignition Switch repair - http://forums.corvetteforum.com/c5-t...ch-repair.html
Before you tear the switch apart, measure the resistance of each power terminal to the switch output terminal and then do the same AFTER you repair the switch.
Bill
That power comes from the IGNITION SWITCH.
My guess is, You have dirty /burnt ignition switch contacts. You can remove the switch and clean and rebent the arms for more contact pressure or just buy a new switch
When the car DIES, actually measure the voltage at the two test points on top of the fuse to ground and see if it read LOW. It SHOULD read battery voltage when ever the key is on.
Here is my post on ignition switch repair:
- C5 ignition Switch repair - http://forums.corvetteforum.com/c5-t...ch-repair.html
Before you tear the switch apart, measure the resistance of each power terminal to the switch output terminal and then do the same AFTER you repair the switch.
Bill
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Forgot to add: If the power from the ignition switch is GOOD, check the GROUND G-401 which is in the drivers rear wheel well on the side of the frame. That ground takes a beating and could be bad.
BC
BC
Thread Starter
Drifting
Joined: Apr 2008
Posts: 1,687
Likes: 86
From: De Pere, WI
Thread Starter
Drifting
Joined: Apr 2008
Posts: 1,687
Likes: 86
From: De Pere, WI
FML....I do believe that I have found the problem -a short to ground is between the fuse panel in the passenger side foot well and the fuse panel under the hood....worst possible spot....
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
A SHORT TO GROUND should BLOW the FUSE. Maybe its a poor connection that cant pass enough current to make the pump work.
Ive see fuse boxes on numerous C5s that the fuse or relay terminal inside the fuse box spreads/deforms enough to make a really POOR connection and causes issues similar to yours.
Break an old fuse in half and use the fuse blade to see if the connection for the fuses female terminal and or relay female terminal in the fuse box has a good tight fit when you PUSH / PULL the blade into the and out of the holder.
Bill
Ive see fuse boxes on numerous C5s that the fuse or relay terminal inside the fuse box spreads/deforms enough to make a really POOR connection and causes issues similar to yours.
Break an old fuse in half and use the fuse blade to see if the connection for the fuses female terminal and or relay female terminal in the fuse box has a good tight fit when you PUSH / PULL the blade into the and out of the holder.
Bill
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Thread Starter
Drifting
Joined: Apr 2008
Posts: 1,687
Likes: 86
From: De Pere, WI
no fuses get blown, and my DAT shows resistance to ground where there should be no path to ground....that said, after ripping **** apart to really get to both of them, I find absolutely nothing wrong with that wire.
Which sends me back to the schematics....and I see the IGN relay is on the same power circuit - a relay that was getting hot along with the F/P relay....imma be pissed if it is a relay that is causing it....probably start throwing **** lol haha.
Which sends me back to the schematics....and I see the IGN relay is on the same power circuit - a relay that was getting hot along with the F/P relay....imma be pissed if it is a relay that is causing it....probably start throwing **** lol haha.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
A damaged wire or connection will do as you describe and "canned" testers will lie about the fault. When you connect the wire to the pump and the voltage disappears it would appear as a grounded/shorted wire.
I had a wire going to my taillights on a truck do a similar thing. I disconnected the harness at the rear connector and the wire measured normal voltage again. I found a green corroded section of wire where the insulation was broken as the harness ran along the bottom of the truck.
Use any kind of load (a headlight bulb would work great) with some pieces or wire and keep testing the wiring at the various connectors until you find where the voltage quits dropping. The failure is between this point and the next bad point downstream.
I had a wire going to my taillights on a truck do a similar thing. I disconnected the harness at the rear connector and the wire measured normal voltage again. I found a green corroded section of wire where the insulation was broken as the harness ran along the bottom of the truck.
Use any kind of load (a headlight bulb would work great) with some pieces or wire and keep testing the wiring at the various connectors until you find where the voltage quits dropping. The failure is between this point and the next bad point downstream.
Last edited by lionelhutz; May 18, 2016 at 01:25 PM.
Thread Starter
Drifting
Joined: Apr 2008
Posts: 1,687
Likes: 86
From: De Pere, WI
Finally got it solved. What made it hard is it wouldnt stay dead for extended periods....As it turns out the factory fuel pump power wire (from the relay in the U/H power distribution panel) to the fuel pump connector had an internal short that caused it to heat up and spike to 3000 ohms. When it cooled down it would work fine.
Ran a temp new wire until I can rip the drive train and engine out this coming winter and replace the wire and route it in the factory location.
Ran a temp new wire until I can rip the drive train and engine out this coming winter and replace the wire and route it in the factory location.
